Deck Stain Calculator
Gallons of stain for any deck size, with coverage rates for semi-transparent, solid, oil-based, and water-based stains. Toggle railings and stairs to include their surface area. Imperial and metric units.
Results
Estimates only. Coverage rates are industry midpoints. Actual yield varies with application method, surface absorbency, and ambient conditions. Buy one extra gallon for touch-ups.
How to use this calculator
- 01Choose Imperial or Metric so deck dimensions, area, and coverage use the unit system you prefer.
- 02Pick the stain type and wood condition. These fill in a practical coverage rate that you can override from the can label.
- 03Enter deck length and width, or use Custom Area when you already know the total surface area.
- 04Set the number of coats, then turn on railings or stairs when those surfaces will be stained too.
- 05Add an optional price per gallon only when you want a rough material cost, then use Gallons Needed as the order quantity.
If you need deck size before estimating stain, use the Deck Calculator, then enter that area here.
Coverage rate reference
Manufacturer-published coverage ranges by stain type and wood condition. Pick a midpoint for estimating, then confirm against the actual can label.
| Stain type | Smooth wood | Rough/weathered |
|---|---|---|
| Semi-transparent | 250–400sq ft/gal | 150–200sq ft/gal |
| Solid | 200–300sq ft/gal | 150–200sq ft/gal |
| Oil-based | 150–200sq ft/gal | 100–150sq ft/gal |
| Water-based | 250–400sq ft/gal | 150–200sq ft/gal |
Frequently asked questions
How much stain do I need for my deck?
Stain needed = (deck area × number of coats) ÷ coverage per gallon, rounded up. For a 12 ft × 16 ft (3.66 m × 4.88 m) deck (192 sq ft / 17.8 m²) with semi-transparent stain on smooth wood (300 sq ft / 27.9 m² per gallon coverage) and 2 coats: 192 × 2 ÷ 300 = 1.28 → 2 gallons. The calculator above adjusts for stain type, wood condition, coats, and any railings or stairs you add.
How do I calculate stain coverage?
Stain coverage is the square footage one gallon will cover at one coat. Semi-transparent on smooth wood: 250-400 sq ft (23-37 m²) per gallon. Solid: 200-300 (19-28 m²). Oil-based: 150-200 (14-19 m²). Water-based: 250-400 (23-37 m²). On rough or weathered wood, coverage drops to about 60% of these numbers because the surface absorbs more product. Check the can label, since manufacturers vary by ±25%. Multiply the area you're staining by the number of coats, then divide by coverage and round up.
How many coats of stain do I need?
Most homeowner jobs use 2 coats. The first coat soaks into the wood and primes it. The second builds the visible finish. Solid stains usually need 2 coats minimum. Semi-transparent often gets by with 1-2 depending on color depth and wood absorbency. Bare or freshly sanded wood may need a third coat to develop full color. Wait the manufacturer's recommended dry time between coats, typically 4-24 hours.
What are the coverage rates by stain type?
Manufacturer ranges, smooth wood: Semi-transparent 250-400 sq ft (23-37 m²) per gallon (most common DIY choice). Solid 200-300 (19-28 m², paint-like, hides grain). Oil-based 150-200 (14-19 m², deepest penetration, most absorbent). Water-based 250-400 (23-37 m², low-VOC, fast dry). On rough or weathered wood, all numbers drop to 100-200 sq ft (9.3-18.6 m²) per gallon. The reference table on this page gives the full grid. Pick a midpoint for estimating, then confirm against the actual can label.
Should I include railings and stairs in my stain estimate?
Yes. Railings and stairs add significant surface area you'll be staining. A typical spindled railing is about 4 sq ft (0.37 m²) of stain surface per linear foot / per 0.3 m (top rail, bottom rail, spindles on both sides). Each deck step adds about 6 sq ft (0.56 m²) (tread top, riser face, stringer sides). For a 12 × 16 ft (3.66 m × 4.88 m) deck with 40 linear ft (12.2 m) of railing and 5 stair steps, the railings alone add 160 sq ft (14.9 m²) and the stairs add 30 sq ft (2.8 m²). That's an extra 190 sq ft (17.7 m²) on top of the 192 sq ft (17.8 m²) deck surface. Use the toggles in the calculator to include them.
What's the difference between oil-based and water-based deck stain?
Oil-based penetrates deeper into the wood, lasts 3-5 years, hides minor surface flaws, and accepts pigments well. Downsides: high VOCs, 24+ hours to dry, restricted in some states. Water-based dries in 2-4 hours, has low VOCs, cleans up with soap and water, lasts 2-3 years, and shows surface defects more clearly. Water-based is the common choice for new decks. Oil-based is preferred for high-traffic decks and older weathered wood that needs deeper penetration. Coverage is similar.
How long should I wait between stain coats?
Manufacturer-specific, but typical guidelines: water-based stain 4-6 hours, oil-based 12-24 hours. Wait until the first coat is touch-dry but not fully cured. Don't apply a second coat in direct sun or above 90°F (32°C), since premature drying causes lap marks. Don't apply after recent rain or with rain in the next 24-hour forecast. Most stain failures come from rushing the dry time or applying in poor weather.
What's the best time of year to stain a deck?
Mid-spring through early fall, when temperatures stay between 50°F (10°C) and 90°F (32°C) day and night, with low humidity and no rain forecast for 24-48 hours. Avoid direct full-sun staining (causes lap marks) and morning dew. Brand-new pressure-treated wood needs 4-8 weeks of weather exposure to dry out before staining. Fresh PT lumber is too wet to absorb stain. Fall is ideal: cooler temps, lower sun angle, fewer bugs landing in wet stain.
How much does it cost to stain a deck?
DIY for a 192 sq ft (17.8 m²) deck: 2 gallons of mid-range stain at $40-50/gal = $80-100, plus brushes, rollers, drop cloths, sandpaper for prep ≈ $30. Total $110-130. Pro labor adds $200-500 depending on prep time (power-washing, sanding, repairs) and complexity. Larger decks scale linearly: figure $0.50-$1 per sq ft (~$5-11 per m²) DIY, $1.50-$3 per sq ft (~$16-32 per m²) pro. High-end stains (Behr Premium, Cabot Australian Timber Oil) run $60-80 per gallon.
Can I use this calculator with metric measurements?
Yes. Pick Metric in the unit selector at the top and inputs switch to meters and m². Coverage rates convert too: semi-transparent on smooth wood ≈ 23-37 m² per gallon / liter equivalent (US gallons are still gallons in metric mode since stain is sold by the gallon globally; 1 US gal = 3.785 L). Total surface area outputs in m². Common conversions: 12 × 16 ft deck = 3.66 m × 4.88 m = 17.8 m². Your unit choice sticks across pages and tabs via localStorage.